Cerebral occlusions that lead to stroke require swift and effective therapy to reduce morbidity and mortality rates associated with the disease. Many current technologies for treating stroke are inadequate because emboli generated during the procedure may travel downstream from the original occlusion and cause ischemia. There is currently a need for a stroke treatment system that provides a swift and efficient treatment for occlusions while simultaneously controlling cerebral flow characteristics.
In the initial stages of stroke, a CT scan or MRI may be used to diagnose the cerebral occlusion, which commonly occurs in the middle cerebral arteries. Many current technologies position a catheter proximal of the occlusion, then deliver clot dissolving drugs to treat the lesion. A drawback associated with such technology is that delivering drugs may require a period of up to six hours to adequately treat the occlusion. Another drawback associated with lytic agents (i.e., clot dissolving agents) is that they often facilitate bleeding.
When removing a thrombus using mechanical thrombectomy devices, it is beneficial to engage the thrombus and remove it as cleanly as possible, to reduce the amount of emboli that are liberated. However, in the event that emboli are generated during mechanical disruption of the thrombus, it is imperative that they be subsequently removed from the vasculature.
Several methods are known for mechanically removing clots to treat cerebral occlusions. For example, U.S. Pat. No. 5,895,398 to Wensel et al. (Wensel) describes a shape-memory coil affixed to an insertion mandrel. The coil is contracted to a reduced profile state within the lumen of a delivery catheter, and the catheter is used to cross a clot. Once the coil is disposed distal of the clot, the coil is deployed and retracted proximally to engage and remove the clot.
A primary drawback associated with the device described in the Wensel patent is that the deployed coil contacts the intima of the vessel, and may damage the vessel wall when the coil is retracted to snare the occlusion. Additionally, the configuration of the coil is such that the device may not be easily retrieved once it has been deployed. For example, once the catheter has been withdrawn and the coil deployed distal of the occlusion, it may be difficult or impossible to exchange the coil for another of different dimensions.
U.S. Pat. No. 5,972,019 to Engelson et al. (Engelson) describes a deployable cage assembly that may be deployed distal of a clot. Like the Wensel device, the device described in the Engelson patent is depicted as contacting the intima of the vessel, and presents the same risks as the Wensel device. In addition, because the distal end of the device comprises a relatively large profile, the risk of dislodging emboli while crossing the clot is enhanced, and maneuverability of the distal end of the device through tortuous vasculature may be reduced.
In view of these drawbacks of previously known devices, it would be desirable to provide apparatus and methods for removal and recovery of thrombi and/or emboli above the carotid bifurcation.
It also would be desirable to provide apparatus and methods that quickly and efficiently treat cerebral occlusions while reducing trauma imposed upon cerebral vessels.
It further would be desirable to provide apparatus and methods for a thrombectomy device that may be used to snare an occlusion and/or rotationally engage fibrin strands of the occlusion.
It still further would be desirable to provide apparatus and methods for a thrombectomy device that selectively may be actuated to deploy to a plurality of deployment configurations while disposed within a treatment vessel.